Process and apparatus for producing bent tubes

ABSTRACT

The invention provides a process and an apparatus for producing elbows having a predetermined degree of curve which comprises melting consumable metallic electrodes supplied into a mold in an electroslag bath inside said mold, coagulating the resulting molten metal inside said mold and continuously pulling out the resulting coagulated metal. The slag bath is of constant depth and the plane area of the slag bath is increased, proceeding from the inner radius to the outer radius of the elbow, to increase the volume of the slag bath in the latter region.

United States Patent [1 1 111 3,910,340

Ujiie [451 Oct. 7, 1975 PROCESS AND APPARATUS FOR PRODUCING BENT TUBES Primary ExaminerFrancis S. Husar Assistant ExaminerJohn E. Roethel [75] Inventor' Aklm Kobe Japan Attorney, Agent, or Firm-Cushman, Darby &

[73] Assignee: Mitsubishi Jukogyo Kabushiki Cushman Kaisha, Tokyo, Japan [22] Filed: May 24, 1974 21 Appl. No.: 473,270 [571 ABSTRACT The invention provides a process and an apparatus for Foreign Appllcatlon Data producing elbows having a predetermined degree of May 25, 1973 Japan 48-57716 curve which comprises melting consumable metallic electrodes supplied into a mold in an electroslag bath [52] U.S. Cl. 164/52; 164/85; 164/252 inside said mold, coagulating the resulting molten [51] Int. Cl? B22D 27/02 metal inside said mold and continuously pulling out [58] Field of Search 164/52, 85, 252, 281 the resulting coagulated metal. The slag bath is of constant depth and the plane area of the slag bath is in- [56] References Cited creased, proceeding from the inner radius to the outer UNITED STATES PATENTS radius of the elbow, to increase the volume of the slag 3,683,997 8/1972 Ujiie et al. 164/52 bath the latter 3,774,667 ll/l973 Ujiie 164/52 FOREIGN PATENTS OR APPLICATIONS 3 Clams 3 Draw 2,131,891 l2/l97l Germany 164/252 to in PROCESS AND v 1 APPARATUS FOR PRODUCING i BENT. TUBES I BACKGROUND or THE INVENTION ,Heretofore, an elbow having a large degree of curvature such as a- 180 or; 90 ,bent elbow has been generally produced by forging or casting. Whereas, in case .an elbow was producedby forging, there have been drawbacks that the cost of a mold for forging is expen- Y sive, the degrees of curvature and thickness of the elbow on the side of an inner radius and on the side of an outer radius become. unequal. Therefore,'there is a problem in terms of quality of the product. Especially in case the material of the pipe is relatively poor in ductility, there a prospect that cracks and fissures are 1; generated in the curved portion during forging. Further, in case the degree of curve is large and the degree of plastic processing becomes large, there is a prospect that the material of the pipe will become of lower quality. In view of these drawbacks, heretofore, a process I for forging a pluralityof divided pipes having relatively small degrees of curve and joining these divided pipes has been adopted..However, by such process, there has i been a problem that number of processing steps increases and the cost becomes remarkably high. On the othenhand, when an elbow is.produced by casting, not

, only unevenness of thickness and eccentricity of a product tends to be brought about, but also occurrence of shrinkage cavities and blowholes peculiar to casting is inevitable. Therefore, these drawbacks must be repaired by processing, which requires time and labor, resulting in high cost, and this trend is especially increasedin a large product required of a high quality.

a after being minutely repaired by processing. However,

because thispipe material is especially inferior in weldability, its repair by processing has been very difficult, complete repair has been impossible and there has been a drawback that many loss claims have been made in respect to the products.

On the other hand, heretofore, as a technology for producing a straight pipe, a process has been known for producing a large straight pipe having a predetermined length which comprises melting consumable metallic electrodes supplied into a mold having a cross-sectional configuration the same as that of a product in an electroslag bath, coagulating the resulting molten metal inside said mold and continuously pulling out this coagulated metal. This process for producing a straight pipe relatively does not bring about a drawback as compared with other conventional processes for producing a straight pipe, being suitable a process for producing a straight pipe especially made of a high quality steel. Therefore, said process is broadly used for producing reformer pipes as reaction pipes in the field of the petrochemical industry.

I noted the 'merit of the aforesaid conventional process for producing a straight pipe, previously developing a special process and a special apparatus 'with a view to eliminating the drawbacks of the aforesaid con ventional technologies for producing' elbows by apply- .ing said technology to production of elbows, said special process. for producing elbows comprising coagulating a moltenmetal obtained by melting a plurality of consumable metallic electrodes supplied at a predetermined speed into a mold in an electroslag bath inside said mold and continuously pulling out the resulting coagulated metal at a predetermined speed, characterized by coagulating said molten metal inside said mold in conformity with a predetermined cross-sectional configuration and curve of an elbow to thereby form unit elbows, at the same time, continuously pulling out said .unit elbows along a curved passage in conformity with thedegree of curve of the elbow.

This developed technology has been realized in production of improved reformer pipes in the field of the petrochemical industry at present, having achieved the expected effect.

I, the present inventor, repeated various experiments with a view to realizing a technology for production capable of producing a thick elbow having a large diameter by this developed technology more advantageously in terms of cost, having made the present invention as a result.

BRIEF EXPLANATION OF DRAWINGS The drawings show one embodiment of the apparatus for practicing the present invention.

FIG. 1 is a longitudinal section showing the invention for melting electrodes and shaping the metal into the resulting product. 7

FIGS. 2 and 3 are drawings showing two specific embodiments showing in a manner like ground plan the arranged states of a plurality of consumable metallic electrode materials.

DETAILED DESCRIPTION OF-THE INVENTION The present invention relates to a process for producing an elbow which comprises melting a plurality of consumable metallic electrode materials supplied at a predetermined speed into a mold consisting of an outer mold and a core mold in an electroslag bath, coagulating the obtained molten metal inside said mold and continuously pulling out this coagulated metal at a predetermined speed from said mold to produce an elbow having a predetermined degree of curve, characterized by making the amount of the slag bath on the side of an outer radius of curve of the elbow inside an upwardly opening portion between said outer mold and said core mold, larger than that on the side of an inner radius of curve of the elbow, at the same time, making the amount of said consumable metallic electrode materials supplied into said slag bath on the side of the producing an elbow which comprises an electrode material member in which a plurality of consumable metallic electrode materials are arranged so that the melted amount is increased from the side of an inner radius of curve of an elbow to the side of an outer radius of curve of the elbow so as to correspond to the cross-sectional configuration of the elbow to be produced and to the unit volume of the elbowper unit angle around the center of curve of the elbow, atthe same time, said electrode material member being so made as to descend at a predetermined speed by a proper drive source. An annular upwardly opening member is disposed directly below said electrode material member, whose volume increases from the side of an inner radius of curve of the elbow to the side of an outer radius of curve of the elbow. An annular central parallel member is provided in communication with said upwardly opening member having a crosssectional area equal to the thickness of the elbow and having a depth becoming deeper from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow. A mold member is provided consisting of an outer mold and a core mold having a fan-wise downwardly opening portion communicating with said central parallel member. A rotary member is provided for pulling out the elbow consisting of a rotary arm made to be rotated around the center of curve of the elbow by a proper drive source. A start piece is provided displacing along a curved passage being in accord with the degree of curve of the elbow in concomitance with rotation of said rotary arm for pulling out unit elbows formed inside said central parallel member. An electricity supply member is provided for supplying electricity between said respective consumable metallic electrode materials 6 and said rotary arm.

Hereinbelow, the present invention will be explained in detail by reference to the accompanying drawings.

In FIGS. 1 to 3, l is an outer mold supported by a supporting member 3 on the fixed frame and 2 is a core mold supported by a supporting member 4 on the fixed frame. These outer mold l and core mold 2 are fixed and supported by said two supporting members 3 and 4 so as to be on a roughly horizontal level containing the center of curve of the elbow product 5 to be formed by the upper tip of a central parallel member I) to be mentioned later during electroslag re-melting of consumable metallic electrodes 6 to be mentioned later. These outer mold 1, core mold 2 and their supporting members 3 and 4 constitute a mold member A.

And an annular space formed by the outer mold l and the core mold 2, in its cross-sectional area, is composed dius r, of curve of the elbow to the side of an outer radius r of curve of the elbow, and a downwardly opening member 0 expanding fan-wise and downwardly from the lower end of said central parallel member I). The cross-sectional area of said upwardly opening member a becomes larger on the side of the outer radius r of curve centering around the center of curve 0 of the elbow 5 than on the side of the inner radius r, of curve. This annular upwardly opening member a is a part becoming a storage means for a slag bath l2 melting consumable metallic electrode materials 6 of an electrode material member B to be mentioned later, the outer mold l and the core mold 2 being so disposed as to cause said slag bath 12 to be located directly below said consumable metallic electrode materials 6. Accordingly, said upwardly opening member a gradually increases its volume from the side of the inner radius r of the elbow to the side of the outer radius r of the elbow, and the amount of the slag bath l2 accumulated inside said upwardly opening member a becomes larger from the inner radius r, to the outer radius r of curve.

The cross-sectional configuration of this upwardly opening member a may be easily formed by, for example, as shown in FIG. 2, sliding the center 0 of the core mold 2 eccentrically from the center 0 of the outer mold l to thereby become gradually large, or by, as shown in FIG. 3, making the both molds 1 and 2 concentric and forming a cross-sectional area on the side of the outer radius r of curve of the core mold 2 smaller than that on the side of the inner radius r of curve.

The annular central parallel member b becomes a storage means for a molten metal produced by electroslag re-melting of the consumable metallic electrode materials 6 inside said upwardly opening member a, at the same time, becomes a place for coagulating said molten metal by the cooling action of said two molds I and 2 to form unit elbows Ap, the cross-sectional area of said annular central parallel member I) is equal to the thickness of the elbow 5, and said annular central parallel member 17 has a depth becoming deeper from the side of the inner radius r of curve of the elbow to the side of the outer radius r of curve of the elbow.

The annular downwardly opening member 0 expands fan-wise as it proceeds downwards from the crosssectional area of said central parallel member b.

Although the means is not shown in detail, the two molds I and 2 are water-cooled.

The numeral 6 denotes a plurality of consumable metallic electrode materials, which are hung perpendicularly by proper electrode holders (not shown) from above the upwardly opening member a of the molds l and 2. The numeral 7 denotes rollers for downwardly supplying these consumable metallic electrode materials 6 at a predetermined speed by a drive source (not shown) suitably controlled so that the lower ends of the respective consumable metallic electrode materials 6 are always located inside the upwardly opening member a of the molds l and 2 during electroslag re-melting of the lower ends of the respective consumable metallic electrode materials 6. Said consumable metallic electrode materials 6, rollers 7 and their drive device constitute an electrode material member B. When electrode materials having the same cross-sectional areas are used as this plurality of consumable metallic electrode materials 6, as shown in FIG. 2 or FIG. 3, on the side of the outer radius r of the elbow, number of the electrode materials is made larger or the electrode materials are so arranged as to make the distance of the adjoining electrode materials closer than on the side of the inner radius r of the elbow. And although not shown, it is permissible to arrange the consumable electrodes 6 having small cross-sectional areas on the side of the inner radius r of the elbow and arrange the consumable electrodes 6 having larger cross-sectional areas to that intervals between adjoining electrodes become the same as they approach the side of the outer radius (2 of the elbow. At any rate, the amount of the consumable metallic electrode materials supplied into the slag bath on the side of the outer radius r of the elbow (p) is made larger than the amount of the consumable metallic electrode materials supplied into the slag bath 12 on the side of the inner radius r of the elbow so as to make said amount (p) correspond to the cross-sectional configuration of the elbow to be produced andto the unit volume of the elbow per unit angle around the center of curve of the elbow.

The numeral 8 denotes a rotary arm whose one end is rotatably pivoted at the center of curve 0 of the product elbow 5 to be rotated around said center 0 of curve by a proper drive device (not shown) at a predetermined angular velocity, said rotary arm is fitted with a start piece 9. Thestart piece 9 is so formed as to have the same shape and dimension those of the elbow 5 to be produced, displacing along a passage having a degree of curve the same as that of the elbow 5 in concomitance with rotation of the rotary arm 8 to be driven by rotation of said drive device to pull out unit elements A p of the elbow 5 from the annular central source of electricity I0 and a power transmission cable 11,.one terminal of the source of electricity is wired to the rotary arm 8 and the other terminal is electrically connected to the respective consumablc metallic electrode materials 6.

An apparatus for practicing the process for the pres- ,entinvention comprises mold member A, electrode material member B, rotary member C for pulling out the product and electricity supply member D.

An explanation will be made about a case of producing an elbow 5 made ofa predetermined metal material by an illustrated apparatus.

Now, the respective consumable metallic electrode materials 6 of the electrode material member A at predetermined positions are supplied at a predetermined speed via the rollers 7, to which electricity is supplied from the electricity supply member D and the electrode materials 6 are caused to descend at a constant speed. At this time, the bottom portion of the central parallel member 17 of the molds l, 2 is blocked by the start piece 9 in advance and a proper molten slag is accumulated in the upwardly opening member a in advance. Then, into this molten slag bath 12 are immersed the consumable metallic electrode materials 6. These consumable metallic electrode materials 6 supply electricity to the start piece 9 via the molten slag to form an electric circult of the source of electricity 10. A so-called electroslag re-melting phenomenon takes place. The tips of the respective consumable metallic electrode materials 6 melt, becoming molten drops 13, dropping in the slag bath I2 and being accumulated in the central parallel member 12. The molten metal 14 is cooled by the molds l, 2 of the mold member A to be solidified. At this time, a part of the molten metal 14 contacting with the start piece 9 is melted and adhered to the start piece. On the other hand, soon the molten metal 14 is accumulated in the central parallel member b and begins to be solidified, as mentioned above, the drive device of the rotary arm 8 rotates at an angular velocity of 66 per unit time, rotating the rotary arm 8 in the direction of the arrow to displace the start piece in the direction of the same arrow. Therefore, the elbow elements Ap cooled and solidified in the mold member A are successively pulled out from the mold member A and an elbow 5 having a predetermined degree of curve is formed.

In this case, the rotating angle per unit time of the rotary arm 8 is properly set up within the range in which the molten metal 14 and the slag bath 12 do not flow out and the core mold 2 is not squeezed by contraction due to coagulation of the unit elbows Ap and pulling out of said unit elbows Ap does not become difficult.

After the elbow product 5 having a predetermined degree of curve is obtained as mentioned above, supply of the consumable metallic electrode materials 6 by the rolls 7 is suspended. At the same time, supply of electricity from the electricity supply member D is discontinued to stop electroslag re-melting. However, the operation of pulling out the elbow product 5 by rotation of the rotary arm 8 is continued until the core mold 2 becomes a state of not being brought over by coagulation and contraction of said elbow product 5, and thereafter, rotation of said rotary arm 8 is stopped and the elbow product 5 is removed from the start piece 9 by proper means to finish one cycle of the steps for producing the elbows. By repeating said cycle, a plurality of elbows having a predetermined degree of curvature is produced one after another.

In the aforesaid electroslag re-melting of the consumable metallic electrode materials 6 in the slag bath 12, from the peculiarity of the shape of the elbow product 5, upon pulling out the elbow product 5 by the rotary arm 8 rotating around the center of curve 0 of the elbow, from the side of the inner radius r of curve of the elbow to the side of the outer radius r of curve of the elbow, naturally the volume of the elbow product increases gradually. Therefore, it is necessary to gradually increase the amount of the molten metal in proportion thereto. However, in the present invention, as shown in FIG. 2 or FIG. 3, a plurality of consumable metallic electrode materials 6 is so arranged that the arrangement proceeds from sparse to dense as it goes from the inner radius r of curve to the outer radius r of curve. Moreover, the cross-sectional area of the upwardly opening member a formed between the outer mold I and the core mold 2 as a storage means for the slag bath 12 is so composed as to increase from the side of the inner radius r of curve to the outer radius r of curve. Therefore, it is possible to sufficiently meet the aforesaid requirement.

Accordingly to the present invention, it is possible to produce elbows made of the desired material easily and swiftly and achieve an effect that elbows of excellent quality having no drawbacks as compared with the prior art may be obtained. In the technology for producing elbowspreviously proposed by the present inventor, a plurality of consumable metallic electrode materials, the electrode materials different in crosssectional area are used, the depth of the upwardly opening member formed between the two molds is made deeper from the side of the inner radius of the elbow to the side of the outer radius of the elbow, and the longitudinal sectional configuration of the central parallel member is made to have a degree of curve the same as that of the elbow to be produced; whereas, in the present invention, a plurality of consumable metallic electrode materials 6 having the equal crosssectional areas, namely, what is commercially available may be used. Accordingly, not only design and establishment of the rolls 7 for supplying said electrode materials 6 are easy, but also by merely providing the core mold 2 eccentrically toward the outer mold l, or by forming the cross-sectional area of the core mold 2 on the side of the outer radius r of curve of the elbow smaller than that on the side of the inner radius r the depth of the upwardly opening member a between the molds l, 2 need not be changed and the longitudinal sectional configuration of the central parallel member [7 between the two molds 1, 2 need not be formed in conformity with the degree of curve of the elbow. Therefore, processing of the mold member A becomes easy and there is an advantage that the over-all cost is remarkably reduced.

I claim:

1. A process for producing an elbow which comprises melting a plurality of consumable metallic electrode materials supplied at a predetermined speed into a mold consisting of an outer mold and a core mold in an electroslag bath, coagulating the obtained molten metal inside said mold and pulling out the coagulated metal at a predetermined speed from said mold to produce an elbow having a predetermined degree of curve, making the amount of the slag bath on the side of an outer radius of curve of the elbow inside an upwardly opening portion between said outer mold and said core mold larger than that on the side of an inner radius of curve of the elbow, at the same time making the amount of the consumable metallic electrode materials supplied into the slag bath on the side of the outer radius of curve of the elbow (p) larger than the amount of the consumable metallic electrode materials supplied into the slag bath on the side of the inner radius of curve of the elbow so as to make said amount (p) correspond to the cross-sectional configuration of the elbow to be produced and the unit volume of the elbow per unit angle around the center of curve of the elbow, characterized by increasing the plane area inside said upwardly opening portion holding the slag bath between said outer mold and said core mold as said portion transfers from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow.

2. An apparatus for producing an elbow which comprises an electrode material member in which a plurality of consumable metallic electrode materials are arranged so that a melted amount is increased from the side of an inner radius of curve of an elbow to the side of an outer radius of curve of the elbow so as to correspond to the cross-sectional configuration of the elbow to be produced and to the unit volume of the elbow per unit angle around the center of curve of the elbow, at the same time, said electrode material member being so made as to descend at a predetermined speed by a proper drive source, an annular upwardly opening member disposed directly below said electrode material member, whose volume increases by increase of the plane area thereof from the side of an inner radius of curve of the elbow to the side of an outer radius of curve of the elbow, an annular central parallel member provided in communication with said upwardly opening member having a cross-sectional area equal to the thickness of the elbow and having a depth becoming deeper from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow, a mold member consisting of an outer mold and a core mold having a fan-wise downwardly opening portion communicating with said central parallel member, a rotary member for pulling out the elbow consisting of a rotary arm made to be rotated around the center of curve of the elbow by a proper drive source and a start piece displacing along a curved passage being in accord with the degree of curve of the elbow in concomitance with rotation of said rotary arm for pulling out unit elbows formed inside said central parallel member and an electricity supply member supplying electricity between said respective consumable metallic electrode materials and said rotary arm.

3. A process according to claim 1, characterized by more densely disposing a plurality of consumable metallic electrode materials as said materials transfer from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow. 

1. A process for producing an elbow which comprises melting a plurality of consumable metallic electrode materials supplied at a predetermined speed into a mold consisting of an outer mold and a core mold in an electroslag bath, coagulating the obtained molten metal inside said mold and pulling out the coagulated metal at a predetermined speed from said mold to produce an elbow having a predetermined degree of curve, making the amount of the slag bath on the side of an outer radius of curve of the elbow inside an upwardly opening portion between said outer mold and said core mold larger than that on the side of an inner radius of curve of the elbow, at the same time making the amount of the consumable metallic electrode materials supplied into the slag bath on the side of the outer radius of curve of the elbow (p) larger than the amount of the consumable metallic electrode materials supPlied into the slag bath on the side of the inner radius of curve of the elbow so as to make said amount (p) correspond to the cross-sectional configuration of the elbow to be produced and the unit volume of the elbow per unit angle around the center of curve of the elbow, characterized by increasing the plane area inside said upwardly opening portion holding the slag bath between said outer mold and said core mold as said portion transfers from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow.
 2. An apparatus for producing an elbow which comprises an electrode material member in which a plurality of consumable metallic electrode materials are arranged so that a melted amount is increased from the side of an inner radius of curve of an elbow to the side of an outer radius of curve of the elbow so as to correspond to the cross-sectional configuration of the elbow to be produced and to the unit volume of the elbow per unit angle around the center of curve of the elbow, at the same time, said electrode material member being so made as to descend at a predetermined speed by a proper drive source, an annular upwardly opening member disposed directly below said electrode material member, whose volume increases by increase of the plane area thereof from the side of an inner radius of curve of the elbow to the side of an outer radius of curve of the elbow, an annular central parallel member provided in communication with said upwardly opening member having a cross-sectional area equal to the thickness of the elbow and having a depth becoming deeper from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow, a mold member consisting of an outer mold and a core mold having a fan-wise downwardly opening portion communicating with said central parallel member, a rotary member for pulling out the elbow consisting of a rotary arm made to be rotated around the center of curve of the elbow by a proper drive source and a start piece displacing along a curved passage being in accord with the degree of curve of the elbow in concomitance with rotation of said rotary arm for pulling out unit elbows formed inside said central parallel member and an electricity supply member supplying electricity between said respective consumable metallic electrode materials and said rotary arm.
 3. A process according to claim 1, characterized by more densely disposing a plurality of consumable metallic electrode materials as said materials transfer from the side of the inner radius of curve of the elbow to the side of the outer radius of curve of the elbow. 